Of course there's a number seven missing, but I think that's probably due to the fact that back when the whole Cylon number thing began, the writers may not have thought up the concept of the seperate five Cylons.

Probably! Too bad there's no logics behind the series of numbers...

The fact we have sentient Centurions now establishes a connection to the old-school Galactica. By the way Cavil is a sort of mix between the old Baltar and the Cylon that was named Mephistopheles.

Any idea about the Fifth, Kashy?